Comment on "A centroid molecular dynamics study of liquid para hydrogen and ortho deuterium" [J. Chem. Phys. 121, 6412 (2004)]

We show that the two phase points considered in the recent simulations of liquid para hydrogen by Hone and Voth lie in the liquid-vapor coexistence region of a purely classical molecular dynamics simulation. By contrast, their phase point for ortho deuterium was in the one-phase liquid region for both classical and quantum simulations. These observations are used to account for their report that quantum mechanical effects enhance the diffusion in liquid para hydrogen and decrease it in ortho deuterium

Polyelectrolyte-Compression Forces between Spherical DNA Brushes

Optical tweezers are employed to measure the forces of interaction within a single pair of DNA-grafted colloids in dependence of the molecular weight of the DNA-chains, and the concentration and valence of the surrounding ionic medium. The resulting forces are short-range and set in as the surface-to-surface distance between the colloidal cores reaches the value of the brush height. The measured force-distance dependence is analyzed by means of a theoretical treatment based on the compression of the chains on the surface of the opposite-lying colloid. Quantitative agreement with the experiment is obtained for all parameter combinations.Comment: 4 pages, 4 figures, 1 table; manuscript submitted to Phys. Rev. Let

Fluid-fluid demixing transitions in colloid--polyelectrolyte star mixtures

We derive effective interaction potentials between hard, spherical colloidal particles and star-branched polyelectrolytes of various functionalities and smaller size than the colloids. The effective interactions are based on a Derjaguin-like approximation, which is based on previously derived potentials acting between polyelectrolyte stars and planar walls. On the basis of these interactions we subsequently calculate the demixing binodals of the binary colloid--polyelectrolyte star mixture, employing standard tools from liquid-state theory. We find that the mixture is indeed unstable at moderately high overall concentrations. The system becomes more unstable with respect to demixing as the star functionality and the size ratio grow.Comment: 24 pages, 9 figures, submitted to Journal of Physics: Condensed Matte

Polyelectrolyte stars in planar confinement

We employ monomer-resolved Molecular Dynamics simulations and theoretical considerations to analyze the conformations of multiarm polyelectrolyte stars close to planar, uncharged walls. We identify three mechanisms that contribute to the emergence of a repulsive star-wall force, namely: the confinement of the counterions that are trapped in the star interior, the increase in electrostatic energy due to confinement as well as a novel mechanism arising from the compression of the stiff polyelectrolyte rods approaching the wall. The latter is not present in the case of interaction between two polyelectrolyte stars and is a direct consequence of the impenetrable character of the planar wall.Comment: 34 pages, 8 figures. Revised version of the manuscript. To appear in J. Chem. Phys. May, 200

Radiation-Induced Graft Immobilization (RIGI): Covalent Binding of Non-Vinyl Compounds on Polymer Membranes

Radiation-induced graft immobilization (RIGI) is a novel method for the covalent binding of substances on polymeric materials without the use of additional chemicals. In contrast to the well-known radiation-induced graft polymerization (RIGP), RIGI can use non-vinyl compounds such as small and large functional molecules, hydrophilic polymers, or even enzymes. In a one-step electron-beam-based process, immobilization can be performed in a clean, fast, and continuous operation mode, as required for industrial applications. This study proposes a reaction mechanism using polyvinylidene fluoride (PVDF) and two small model molecules, glycine and taurine, in aqueous solution. Covalent coupling of single molecules is achieved by radical recombination and alkene addition reactions, with water radiolysis playing a crucial role in the formation of reactive solute species. Hydroxyl radicals contribute mainly to the immobilization, while solvated electrons and hydrogen radicals play a minor role. Release of fluoride is mainly induced by direct ionization of the polymer and supported by water. Hydrophobic chains attached to cations appear to enhance the covalent attachment of solutes to the polymer surface. Computational work is complemented by experimental studies, including X-ray photoelectron spectroscopy (XPS) and fluoride high-performance ion chromatography (HPIC)

Focus: Implementing participation - Advancement of social services in analog and digital spaces

Digitale Informations- und Kommunikationstechnologien gewinnen als fester Bestandteil zunehmend Bedeutung in den alltäglichen Lebenswelten einer wachsenden Zahl von Menschen. Ihre Entwicklung und selbstverständliche Nutzung schreiten in einem immer rasanteren Tempo voran; die vielfältigen Anwendungsmöglichkeiten adressieren längst alle Lebensbereiche. Während der Digitalisierung von Kommunikationsprozessen zuweilen demokratisierende Kräfte zugesprochen werden, scheint eine kritische Reflexion möglicher Potentiale und Auswirkungen digitaler Informations- und Kommunikationstechnologien auf Teilhabedynamiken in unterschiedlichen Lebensbereichen dringend erforderlich. Die Autorinnen und Autoren möchten mit dieser SI:SO-Schwerpunktausgabe einen Beitrag zu einer kritischen Reflexion digitaler Innovationen und ihrer Auswirkungen auf die zukünftige Gestaltung sozialer Dienste leisten. Mit der zweisprachigen Ausgabe ist zudem die Hoffnung verbunden, diesen Beitrag auch einem europäischen und weltweiten Publikum zugänglich zu machen.Digital information and communications technologies are becoming an increasingly important part in everyday life of a growing number of people. Their development and natural use are progressing even faster with a wide range of possible applications addressing all areas of life. While the digitization of communication processes is sometimes said to have democratizing forces, critical reflection on the potential and impact of digital information and communication technologies on participation dynamics in different areas of life seems urgently needed. The Authors would like to contribute to a critical reflection on digital innovations and their impact on the future design of social services. The bilingual edition further aims to make this contribution accessible to a European and global audience

Planning and Development of Social Services for Persons with Disabilities

Soziale Dienste zur Unterstützung von Menschen mit Behinderungen haben sich in den letzten Jahren dynamisch entwickelt und unterliegen auch aktuell einem erheblichen Veränderungsdruck. Die Forschungsarbeiten, die in diesem Band versammelt sind, haben die Entwicklung hin zu einer inklusionsorientierten Unterstützung in zahlreichen Projekten auf unterschiedlichen Ebenen aktiv begleitet.Social services to support persons with disabilities have developed dynamically in recent years and are currently subject to considerable pressure to change. The research work collected in this volume has actively accompanied the development towards inclusion-oriented support in numerous projects at different levels

A genome-wide genetic map of NB-LRR disease resistance loci in potato

Like all plants, potato has evolved a surveillance system consisting of a large array of genes encoding for immune receptors that confer resistance to pathogens and pests. The majority of these so-called resistance or R proteins belong to the super-family that harbour a nucleotide binding and a leucine-rich-repeat domain (NB-LRR). Here, sequence information of the conserved NB domain was used to investigate the genome-wide genetic distribution of the NB-LRR resistance gene loci in potato. We analysed the sequences of 288 unique BAC clones selected using filter hybridisation screening of a BAC library of the diploid potato clone RH89-039-16 (S. tuberosum ssp. tuberosum) and a physical map of this BAC library. This resulted in the identification of 738 partial and full-length NB-LRR sequences. Based on homology of these sequences with known resistance genes, 280 and 448 sequences were classified as TIR-NB-LRR (TNL) and CC-NB-LRR (CNL) sequences, respectively. Genetic mapping revealed the presence of 15 TNL and 32 CNL loci. Thirty-six are novel, while three TNL loci and eight CNL loci are syntenic with previously identified functional resistance genes. The genetic map was complemented with 68 universal CAPS markers and 82 disease resistance trait loci described in literature, providing an excellent template for genetic studies and applied research in potato

Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles can providemultiple benefits for biomedical applications in aqueous environments such asmagnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles’ surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.status: publishe